Drum washing machine

ABSTRACT

A drum washing machine includes a water tub ( 10 ), a rotating tub ( 14 ) mounted in the water tub ( 10 ) to be rotated about a transverse axis, an elastic support ( 11 ) for elastically supporting the water tub ( 14 ), and an auxiliary baffle ( 23 ) formed on the inner peripheral wall of the rotating tub ( 14 ) so as to be close to one of the end plates of the rotating tub and away from the other end plate of the rotating tub ( 14 ). The auxiliary baffle ( 23 ) extends in a direction of axis of the rotating tub ( 14 ). The auxiliary baffle ( 23 ) moves laundry in the rotating tub ( 14 ) near a center of gravity of a member of vibration system applying load to the elastic support ( 11 ).

TECHNICAL FIELD

This invention relates to a drum washing machine with a rotating tubrotated about a transverse axis.

BACKGROUND ART

A drum washing machine includes a rotating tub rotated about atransverse or substantially horizontal axis and a water tubaccommodating the rotating tub. The rotating tub has an inner peripheralwall provided with a plurality of baffles raising laundry. In each ofwash and rinse steps, water is reserved in the water tub and therotating tub accommodating laundry is rotated at low speeds. As aresult, the laundry in the rotating tub is raised and then falls downrepeatedly, whereby the laundry is washed by a beat-wash manner. In adehydration step, the rotating tub is rotated at low speeds so thatwater contained in the laundry is removed to some extent and thereafter,the rotational speed of the rotating tub is gradually increased up to amaximum speed so that the laundry is centrifugally dehydrated.

When laundry is put into the rotating tub to be one-sided such that thelaundry is one-sided in the rotating tub at the time of start of washingoperation, the one-sided state of laundry cannot be solved even after awashing step progresses. A great vibration is produced in thedehydration step when laundry is one-sided particularly near both axialends in the interior of the rotating tub. In the conventional drumwashing machines, accordingly, a liquid balancer is provided to restrainproduction of great vibration or noise due to an unbalanced state oflaundry or the rotating tub is rotated in the normal and reversedirections at low speeds in an initial stage of the dehydration step sothat the unbalanced state is corrected. However, even when theaforementioned method is adopted, vibration or noise cannot sufficientlybe suppressed in large types of drum washing machines with large washingcapacity.

JP-A-2002-31598 proposes a construction in which auxiliary baffles areprovided on a rear end plate of the rotating tub in a drum washingmachine with a rotating tub inclined frontward upward in order thatreduction in the cleaning performance due to the unbalanced state oflaundry may be restrained. Laundry tends to be easily one-sided to aninner interior of the rotating tub when the rotating tub is inclinedfrontward upward. According to the foregoing construction, the laundryone-sided in the inner interior of the rotating tub is sufficientlyagitated, washing unevenness can be restrained.

Patent document: JP-A-2002-31598

DISCLOSURE OF THE INVENTION PROBLEM TO BE OVERCOME BY THE INVENTION

However, the aforementioned auxiliary baffles are provided for thepurpose of agitating laundry which is located at the inner interior ofthe rotating tub and cannot be agitated by the conventional baffles.That is, even when the auxiliary baffles are provided, the washingoperation is continued while the problem of laundry being one-sided tothe inner interior of the rotating tub remains unsolved. As a result,large vibration or noise tends to occur easily in the dehydration step.

Therefore, an object of the present invention is to provide a drumwashing machine which can suppress occurrence of vibration or noise inthe dehydration step.

MEANS FOR OVERCOMING THE PROBLEM

The present invention provides a drum washing machine comprising a watertub, a rotating tub provided in the water tub to be rotated about atransverse axis, elastic supporting means for elastically supporting thewater tub, and an auxiliary baffle provided on an inner peripheral wallof the rotating tub so as to be close to one of both axial end plates ofthe rotating tub and spaced away from the other end plate of therotating tub, the auxiliary baffle extending in a direction of axis ofthe rotating tub, characterized in that the auxiliary baffle moveslaundry in the rotating tub near a center of gravity of a member ofvibration system applying load to the elastic supporting means.

In the above-described construction, the auxiliary baffle has aninclined face inclined at the inner peripheral wall side from one endplate side of the rotating tub to the other end plate side.

EFFECT OF THE INVENTION

Upon rotation of the rotating tub in a washing operation, laundrylocated both axial ends of the rotating tub is moved to a centralinterior of the rotating tub by the action of the auxiliary baffle.Consequently, since unbalance is prevented from occurring at both axialends of the rotating tub during the dehydrating step, occurrence oflarge vibration can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a drum washing machine in accordancewith one embodiment of the present invention;

FIG. 2 is a longitudinal side section of the drum washing machine;

FIG. 3 is a perspective view of a rotating tub with a drum lid beingeliminated;

FIG. 4 is an enlarged perspective view of an auxiliary baffle;

FIG. 5 is a view explaining the difference between a centrifugal forceapplied to laundry located at an outer peripheral position and acentrifugal force applied to laundry located at an inner peripheralposition in the rotating tub;

FIG. 6 is a view explaining a centrifugal force applied to laundry andmoment of inertia about the center of gravity;

FIG. 7 is a graph showing differences in entanglement rates uponcompletion of drying between a case where an auxiliary baffle isprovided and a case where no auxiliary baffle is provided;

FIG. 8 is a graph showing differences in vibration produced in thedehydration step between a case where an auxiliary baffle is providedand a case where no auxiliary baffle is provided and further betweendifferent sizes of auxiliary baffles;

FIG. 9 is a graph showing differences in the vibration amplitude when anauxiliary baffle 23 takes different values of height; and

FIG. 10 is a graph showing differences in the vibration amplitude whenan auxiliary baffle 23 takes different values of axial dimension.

DESCRIPTION OF REFERENCE SYMBOLS

Reference symbol 1 designates a drum washing machine, 10 a water tub, 11suspension (elastic supporting means), 14 a rotating tub, 15 a tubshaft, 20, 21 and 22 main baffles, 23 an auxiliary baffle, and 23 a and23 b inclined faces.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will be described in more detail with reference to theaccompanying drawings. FIGS. 1 to 10 illustrate one embodiment of theinvention. The invention is applied to a drum washing machine of theopen top type in the embodiment. Referring to FIGS. 1 and 2, a washingmachine 1 in accordance with the embodiment of the invention comprises abase plate 2, an outer cabinet 3 fixed on the base plate 2 and a topcover 5 attached to an upper part of the outer cabinet 3 and having anaccess opening 4 through which laundry is put into and taken out of arotating tub. The outer cabinet 3 comprises a main body 6 and a frontpanel 7. The top cover 5 is provided with an outer lid 8 opening andclosing the access opening 4. The outer lid 8 is formed into a foldabletype and includes a front lid 8 a and a rear lid 8 b. An operation panel9 is provided on a right front of the top cover 5.

A generally cylindrical water tub 10 is elastically supported by aplurality of suspensions 11 (corresponding to elastic supporting means)in the outer cabinet 3. Each suspension 11 comprises a damper 11 a and asuspension coil spring 11 b. The water tub 10 has an opening 13 formedin an upper part thereof. The opening 13 is opened and closed by aninner lid 12. When the opening 13 is closed by the inner lid 12, awatertight seal is provided between the inner lid 12 and the opening 13.

A generally cylindrical rotating tub 14 is rotatably supported in thewater tub 10. The rotating tub 14 has a diameter of about 520 mm and anaxial dimension of about 400 mm. The rotating tub 14 serves as a washingtub, dehydrating tub and drying tub. The rotating tub 14 has aperipheral wall formed with a number of small holes (not shown). A pairof substantially horizontally extending tub shafts 15 (shown only inFIG. 5) are mounted on left and right end plates of the rotating tub 14respectively. The tub shafts 15 are rotatably supported on bearings (notshown) provided on the left and right end plates of the water tub 10respectively. The tub shafts 15 extend substantially horizontally. Anelectric motor (not shown) is mounted on the left end plate of the watertub 10. The motor has a rotating shaft coupled to an end of the tubshaft 15 supported by the left end plate of the water tub 10. Thus, therotating tub 14 is directly driven by the motor. Reference symbol “O” inFIG. 2 designates a center of the tub shaft 15, namely, an axis passingthrough center of rotation of the rotating tub 14.

The peripheral wall of the rotating tub 14 is formed with an opening 17(see FIG. 3) opened and closed by a drum lid 16. The drum lid 16comprises a main plate 18 pivoting about a fulcrum 18 a (FIG. 2) and anauxiliary plate 19 pivoting about a fulcrum 19 a. The main and auxiliaryplates 18 and 19 are linked by a link mechanism (not shown) so as to beopened and closed. When the drum lid 16 is closed (state as shown inFIG. 2), a distal end of the main lid 18 overlaps a distal end of theauxiliary plate 19. The drum lid 16 is held in the closed state bylocking means (not shown). When the rotating tub 14 is stationary, theopening 17 is opposed to the opening 13 of the water tub 10.

Referring to FIGS. 2 and 3, a plurality of, for example, three, mainbaffles 20 to 22 each of which has a generally triangular section areprovided on the inner peripheral wall of the rotating tub 14. The mainbaffles 20 to 22 are disposed substantially at regular intervals. Thetwo main baffles 20 and 21 are disposed at both sides of the opening 17so as to sandwich the opening 17. Each of these main baffles has alength set at about 230 mm. The other main baffle 22 is disposed so asto be opposed to the opening 17 with the center of rotation of the tub14 being located therebetween. The main baffle 22 has a length set atabout 320 mm. Each of the main baffles 20 to 22 has a height (radialdimension of the rotating tub 14) set at about 30 mm. The main baffles20 to 22 are disposed near the axial middle of the inner peripheral wallso as to be spaced away from both end plates by the same distance. Thelonger main baffle 22 encloses a counterweight to balance itself withthe drum lid 16 although the counterweight is not shown.

Referring to FIGS. 2 to 4, two pairs of auxiliary baffles 23 (first andsecond baffles) are provided between the main baffles 20 and 21 andbetween the main baffles 21 and 22 on the inner peripheral wall of therotating tub 14 respectively. The auxiliary baffles 23 of each pair aredisposed on the left and right ends of the inner peripheral wall of therotating tub 14 respectively so as to be axially opposed to each other.Each auxiliary baffle 23 is fixed to the inner peripheral wall of therotating tub 14 by screws so as to be in contact with the left or rightend plate of the tub. Each auxiliary baffle 23 generally has the shapeof a triangular pyramid and is tapered from either end plate of therotating tub 14 toward the axial middle of the inner peripheral wall ofthe tub. Each auxiliary baffle 23 has a narrow inclined face 23 aextending from either one end plate of the rotating tub 14 toward theother end plate and inclined to the inner peripheral wall side. Eachauxiliary baffle 23 further has triangular inclined faces 23 b extendingfrom the inclined face 23 a toward the inner peripheral wall of therotating tub 14 and inclined to both peripheral sides respectively.

Reference symbol “H1” designates a height of a portion of each auxiliarybaffle 23 in contact with either end plate of the rotating tub 14(radial dimension of the rotating tub 14) as shown in FIG. 4. The heightH1 is set at about 65 mm. Further, reference symbol “H2” designates alength of the inner peripheral wall of the rotating tub 14. The lengthH2 is set at about 100 mm. The inner peripheral wall of the rotating tub14 has an opening (not shown) formed in a portion thereof locatedbetween the main baffle 22 and the auxiliary baffle 23 disposed betweenthe baffles 21 and 22. Laundry which has entered a space between thewater tub 10 and the rotating tub 14 is recovered through the opening.The opening is closed by a cover 25.

In the outer cabinet 3 are provided a water supply for supplying waterinto the water tub 10, drainage for draining water from the water tub10, and a drier for dehumidifying and heating air in the rotating tub14, returning hot air into the rotating tub 14 thereby to dry laundry,although not shown. In the embodiment, of components of the drum washingmachine 1, members of the vibration system include the water tub 10,rotating tub 14, electric motor, etc. applying load to the suspensions11. The members of the vibration system have a center of gravity locatedat an axial middle of the rotating tub 14.

The operation of the drum washing machine will now be described. Anoverall operation of the drum washing machine is controlled by a controlmicrocomputer (not shown) accommodated in the outer cabinet 3. Whenlaundry is put into the rotating tub and start of operation isinstructed, the control microcomputer carries out steps of a previouslydetermined operation course. For example, when the washing operationstarts with a standard operation course being set, the controlmicrocomputer carries out wash, rinse, dehydration and drying stepssequentially.

More specifically, in each of the wash and rinse steps, the controlmicrocomputer drives the water supply so that water is supplied into thewater tub 10 until a predetermined water level is reached, andthereafter, the control microcomputer drives the motor so that therotating tub 14 is rotated alternately in the normal and reversedirections at low speeds. When the motor is to be stopped, the controlmicrocomputer controls the motor so that the opening 17 is opposed tothe opening 13 of the water tub 17. When the rotating tub 14 is rotatedalternately in the normal and reverse directions at low speeds, laundryaccommodated in the rotating tub 14 is raised with the water in thewater tub 10 by the main baffles 20 to 22 and thereafter, falls downrepeatedly, whereby wash and rinse steps are carried out. In this case,since the laundry contains a sufficient amount of water and areaccordingly heavy, the laundry located at both axial ends of therotating tub 14 can be moved near the main baffles 20 to 22 by theauxiliary baffles although the auxiliary baffles 23 have a smalleraction of raising the laundry than the main baffles 20 to 22.Furthermore, when the laundry is moved near the main baffles 20 to 22 bythe auxiliary baffles 23, a mechanical force is applied to the laundrylocated at each axial end of the rotating tub 14 such that the laundryis pressed, whereupon the cleaning performance can be improved.

In the dehydration step, the control microcomputer drives the drainageso that water is drained from the water tub 10 and thereafter drives themotor so that the rotating tub 14 is rotated in one direction at a lowspeed of about 40 rpm. The laundry containing a large amount of waterupon completion of draining are located at a lower interior of therotating tub 14. Accordingly, when the rotating tub 14 is rotated at thelow speed, the laundry is raised by the main baffles 20 to 22 and thenfalls down repeatedly. As a result, a certain amount of water containedin the laundry is extracted.

The control microcomputer then drives the motor so that the rotating tub14 is rotated at a speed ranging from 60 to 80 rpm in one direction. Inthis case, the laundry is moved in the rotating tub 14 by the mainbaffles 20 to 22 and auxiliary baffles 23, sticking uniformly to anentire inner peripheral wall of the rotating tub 14. More specifically,the laundry located near an axially central interior of the rotating tub14 is raised by the main baffles 20 to 22. The laundry then sticks tothe inner peripheral wall of the rotating tub 14 or falls down dependingupon a magnitude of centrifugal force applied to the laundry.

FIG. 5 explains a centrifugal force applied to laundry S in the rotatingtub 14. A centrifugal force F applied to the laundry S is defined as:F=m·r·ω ²   (1)where reference symbol “r” designates a distance from the centralrotation axis O of the rotating tub 14 to the center of gravity of thelaundry S, reference symbol “m” the mass of laundry S and referencesymbol “ω” a turning angle velocity. The centrifugal force F is inproportion to the distance r as shown in equation (1). When a largeamount of laundry S is accommodated in the rotating tub 14, a distancer1 from the center of gravity of laundry S1 located at the outerperipheral side to the central rotation axis O is larger than a distancer2 from the center of gravity of laundry S2 located at the innerperipheral side to the central rotation axis O (r1>r2). Accordingly, acentrifugal force applied to the laundry S1 becomes larger than acentrifugal force applied to the laundry S2. As a result, of the laundryraised by the main baffles 20 to 22, the laundry located at the outerperipheral side sticks to the inner peripheral wall without fallingdown, whereas the laundry located at the inner peripheral side fallsdown. Consequently, the laundry in the rotating tub 14 is graduallydispersed, sticking to the inner peripheral wall.

On the other hand, water has been extracted from the laundry located ateach axial end side of the rotating tub 14 such that the laundry has alight weight. Accordingly, the laundry is raised by the auxiliarybaffles 23. In this case, since each auxiliary baffle 23 has the shapeof the triangular pyramid, the laundry is moved by the inclined faces 23a near the axial center of the rotating tub 14 and further moved by theinclined faces 23 b from the peripheral both sides of each auxiliarybaffle 23 near the axial center. Consequently, the laundry is gatherednear the axial center of the rotating tub 14. The laundry gathered nearthe axial center of the rotating tub 14 is caused to stick uniformly tothe inner peripheral surface of the rotating tub 14 by the action of theabove-described main baffles 20 to 22.

Thus, the laundry in the rotating tub 14 is gradually dispersed to theentire inner peripheral wall surface such that the unbalanced conditionis reduced. As the result of the foregoing operation, an amount oflaundry located near the axial center of the rotating tub 14 becomeslarger than an amount of laundry located near both ends of the tub.

When determining that the laundry has stuck uniformly to the innerperipheral wall of the rotating tub 14, the control microcomputer drivesthe motor so that the rotational speed of the rotating tub 14 isincreased to about 100 rpm. This determination is made, for example, bydetecting variations in the rotational speed (rotation unevenness) ofthe motor during one turn of the rotating tub. The rotational speed (100rpm) is set at a rotational speed at which the centrifugal force appliedto all the laundry in the tub 14 exceeds the gravitational acceleration.Accordingly, in this case, the rotating tub 14 is rotated while all thelaundry has stuck to the inner peripheral wall of the rotating tub 14.

Subsequently, the control microcomputer drives the motor so that therotational speed of the tub 14 is increased to a maximum speed rangingfrom 900 to 1200 rpm. As a result, the laundry sticking to the innerperipheral wall of the rotating tub 14 is rotated together with therotating tub 14, whereby the laundry is centrifugally dehydrated. Whenlarge vibrations are produced at a plurality of resonance pointsappearing during the increase in the rotational speed of the tub 14 from100 rpm to the maximum speed, the control microcomputer decreases therotational speed of the tub 14 so that the laundry in the tub 14 ismoved, so that an operation is carried out to correct the unbalancedcondition resulting in the resonant vibration. After correction of theunbalanced condition, the control microcomputer again increases therotational speed of the rotating tub 14 up to the maximum speed.

FIG. 5 explains vibration produced during dehydration. The magnitude ofthe vibration produced during dehydration depends upon an excitingforce. The magnitude of the exciting force depends upon a centrifugalforce applied to the laundry S and moment of inertia M about the centerof gravity acting upon the laundry S. The moment of inertia M is definedas:M=F·L=m·r·ω ² ·L   (2)where reference symbol “G” designates a plane which passes the center ofgravity of the vibration system and is perpendicular to the centralrotation axis O, and reference symbol “L” designates a distance from theplane G to the center of gravity of the laundry S. Reference symbol “F”designates the centrifugal force acting upon the laundry as describedabove. As shown by equation (2), the moment of inertia M is inproportion to the distance r and distance L. Further, the centrifugalforce F is in proportion to the distance r as described above.Accordingly, the vibration due to the unbalanced condition near theaxial center of the rotating tub 14 becomes smaller than the vibrationdue to the unbalanced condition at each of both axial ends in therotating tub 14.

Since the laundry is gathered near the axial center of the rotating tub14 in the embodiment, the unbalanced condition exists near the axialcenter in the interior of the rotating tub 14, namely, near the centerof gravity of the vibration system. Consequently, vibration produced inthe dehydration step can be reduced as compared with the conventionaldrum washing machine in which the unbalanced condition occurs at each ofaxial ends of the rotating tub.

In the drying step, the control microcomputer drives the motor so thatthe rotating tub 14 is rotated alternately in the normal and reversedirections at low speeds and drives the drier. As a result, hot air issupplied into the rotating tub 14 so that moisture contained in thelaundry is extracted. Air containing moisture is dehumidified and heatedand thereafter, again returned into the rotating tub 14. The laundry inthe rotating tub 14 is dried by the aforementioned air circulation.

Furthermore, when the rotating tub 14 is rotated alternately in thenormal and reverse directions at low speeds, the laundry in the tub israised by the main baffles 20 to 22 and then caused to fall down by thehot air flowing in the tub while spreading. Further, the auxiliarybaffles 23 moves the laundry fallen in the spread state near the axialcenter of the rotating tub 14. In other words, the laundry is caused tomove in the rotating tub 14 while being dispersed and gathered.Consequently, since the laundry is efficiently brought into contact withthe hot air flowing in the rotating tub 14, the drying efficiency can beimproved.

An experiment conducted by the inventors shows that when laundry isagitated by the main baffles 20 to 22 and auxiliary baffles 23, twistingand entanglement of laundry can be reduced upon completion of the dryingstep.

FIG. 7 is a bar graph showing comparison of entanglement rates at thetime of completion of the drying step between the drum washing machine(P in FIG. 7) having the main baffles 20 to 22 and auxiliary baffles 23and a drum washing machine (Q in FIG. 7) having only the main baffles 20to 22. The Axis of abscissas represents an amount of laundry and theaxis of ordinates represents an entanglement rate. The entanglement rateT (%) is obtained from the following equation:T={(T1−T0)/T0}×100where T0 and T1 are averages of time periods in sec. required for takingall the laundry comprised of a plurality of pieces of bleached cottoncloth out of the rotating tub 14 before and after a washing operationone by one to the rhythm with a metronome respectively. As obvious fromFIG. 7, an entanglement rate is lower in the drum washing machine withthe auxiliary baffles 23 than in a washing machine without auxiliarybaffles 23.

The following effects can be achieved from the foregoing embodiment.Since the rotating tub 14 is provided with the auxiliary baffles 23,laundry can be moved near the axial center in the rotating tub 14 duringthe dehydration step, namely, near the center of gravity of thevibration system. Consequently, occurrence of vibration and noise can berestrained in the dehydration step. Further, since the laundry locatedat both axial ends of the tub 14 is efficiently moved near the axialcenter by the auxiliary baffles 23, an operating time for correction ofunbalanced condition can be shortened.

In the drying step, laundry is moved in the rotating tub 14 while beingdispersed and gathered by cooperation of the main baffles 20 to 22 andthe auxiliary baffles 23. Particularly in the foregoing embodiment,since the main baffles 20 to 22 and the auxiliary baffles 23 are spacedfrom each other, these baffles efficiently cooperate to move thelaundry. Consequently, the drying efficiency can be improved and theentanglement of laundry can be reduced. Further, the experimentconducted by the inventors shows that an amount of wrinkle produced onthe laundry at the time of completion of the drying is smaller in thedrum washing machine with the auxiliary baffles 23 than in the drumwashing machine without auxiliary baffles. This results from the reducedentanglement rate in the drying step. Accordingly, the laundry can befinished in a more favorable condition.

FIG. 8 shows the results of an experiment conducted by the inventorsregarding differences in amplitude of vibration produced duringdehydration depending upon provision or non-provision of the auxiliarybaffles 23 and the sizes of the tub. In FIG. 8, the axis of abscissasrepresents an amount of laundry (kg) and the axis of ordinatesrepresents amplitude of vibration (mm). Further, in FIG. 8, polygonallines P1 to P4 represent the drum washing machine with the main baffles20 to 22 and auxiliary baffles 23, and polygonal line Q represents adrum washing machine with only the main baffles 20 to 22. (60 mm, 40mm), (60 mm, 65 mm), (100 mm, 40 mm) and (100 mm, 65 mm) arecombinations of the lengths (H1, H2; and see FIG. 4) of auxiliarybaffles of the drum washing machine corresponding to the polygonal linesP1 to P4.

As obvious from FIG. 8, the amplitude of vibration produced duringdehydration is smaller in the drum washing machine with the main baffles20 to 22 and auxiliary baffles 23 than in the drum washing machine withonly the main baffles 20 to 22. Furthermore, of the drum washingmachines with auxiliary baffles 23, the drum washing machine asrepresented by the polygonal line P4, namely, the drum washing machineof the embodiment has the smallest amplitude. Consequently, thevibration produced during dehydration can be reduced to a large extent.

The invention should not be limited by the foregoing embodiment but maybe modified as follows. The height (H1) and the length (H2) of eachauxiliary baffle 23 should not be limited by the above-describeddimensions. FIGS. 9 and 10 are graphs made on the basis of theexperimental results of FIG. 8 in order that differences in thevibration amplitude due to the differences in the height and the lengthof each auxiliary baffle 23 may be investigated. More specifically, thegraph of FIG. 9 is made on the basis of the experimental results(corresponding to polygonal lines P1 and P2 in FIG. 8) regarding thedrum washing machine with the auxiliary baffles 23 having the samelength (60 mm) and different heights. The Axis of abscissas in FIG. 9represents the height of each auxiliary baffle 23 in mm and the axis ofordinates represents a reduced amount of amplitude in the drum washingmachine without auxiliary baffles. Further, the graph of FIG. 10 is madeon the basis of the experimental results (corresponding to polygonallines P1 and P3 in FIG. 8) regarding the drum washing machine with theauxiliary baffles 23 having the same height (40 mm) and differentlengths. The Axis of abscissas in FIG. 10 represents the length of eachauxiliary baffle 23 in mm and the axis of ordinates represents a reducedamount of amplitude in the drum washing machine without auxiliarybaffles in mm. Further, polygonal lines K1 to K4 in FIGS. 9 and 10 aremade on the basis of data in the cases where an amount of laundry is 1kg, 3 kg, 5 kg and 8 kg.

As obvious from FIGS. 9 and 10, the reduced amount of vibration isincreased as the height of each baffle 23 becomes larger or as thelength of each baffle 23 becomes larger. In consideration of thevariations of about 0.5 mm in the amplitude of vibration produced duringthe dehydration step, the vibration reduction effect becomes significantwhen a reduced amount of vibration exceeds 0.5 mm. Accordingly,regarding four amounts of laundry used in the experiment, each auxiliarybaffle for which a reduced amount of vibration exceeds 0.5 mm has theheight of not less than about 30 mm and the length of not less thanabout 50 mm.

The height of each auxiliary baffle affects its action of raisinglaundry and has a relation with a thickness of the laundry. Since ageneral thickness of laundry is about 30 mm, it is preferable to set theheight of each auxiliary baffle at 30 mm or above. The length of eachbaffle affects its action of moving laundry from the axial ends of therotating tub near the center of gravity of the vibration system. Thelength of each baffle also has a relation with an axial dimension of therotating tub and a distance from an end of the rotating tub to thecenter of gravity of the vibration system. In the foregoing embodiment,the axial dimension of the rotating tub 14 is 400 mm and the distancefrom the end plate of the rotating tub 14 to the center of gravity is200 mm. Accordingly, the length of each auxiliary baffle from which asignificant vibration reduction can be achieved is not less than oneeighth of the length of the rotating tub 14 and not less than a quarterof the distance from the end plate to the center of gravity. In thiscase, the auxiliary baffles 23 need to be disposed in a region of theinner peripheral wall surface of the rotating tub 14 from the plane G(see FIG. 5).

Further, the auxiliary baffles disposed at both axial sides of therotating tub may or may not be opposed to each other. Further, theauxiliary baffles may be provided on the inner peripheral wall so as tobe located close to the end plate of the rotating tub but need not be incontact with the end plate.

In a drum washing machine with the central rotation axis of the rotatingtub is inclined forwardly upward, auxiliary baffles located close to thefront end plate may be provided on the front of the inner peripheralwall of the rotating tub in order that the laundry in the rotating tubmay be one-sided to the inner or rear interior of the rotating tub.

In a drum washing machine in which the center of gravity of thevibration system is shifted from the axial center of the rotating tub,it is preferred that a pair of auxiliary baffles axially opposed to eachother have different axial dimensions respectively. More specifically,when the center of gravity is one-sided to one side relative to theaxial center of the rotating tub, the auxiliary baffle disposed at anaxial one side of the peripheral wall should have a smaller axialdimension than the auxiliary baffle disposed at the other side of theperipheral wall. However, each auxiliary baffle needs to be disposed inthe region between the plane G passing the center of gravity and the endplate.

Each baffle may be made by pressing the peripheral wall or the endplate. In this case, since the auxiliary baffles may be formedintegrally with the rotating tub, the number of assembly steps can bereduced. Furthermore, each auxiliary baffle should not be limited to theshape of triangular pyramid but may be formed into the shape of asemicircular pyramid.

The invention may be a drum washing machine having an access opening inthe front. In this case, auxiliary baffles may be provided on a frontpart of the peripheral wall of the rotating tub so as to be locatedclose to the front end plate of the rotating tub. The rotating tub withan opening in the front is rotated about a rotational shaft provided onthe rear thereof. Accordingly, when laundry gathers to the frontinterior in the rotating tub, the vibration caused by the rotating tubis increased and a large moment is applied to the rotational shaft or ashaft bearing. However, when the auxiliary baffles are provided on thefront part of the peripheral wall of the rotating tub, the laundry canbe prevented from gathering to the front interior of the rotating tuband accordingly, an occurrence of vibration can be suppressed.

APPLICABILITY OF INDUSTRIAL USE

As obvious from the foregoing, since the drum washing machine of thepresent invention can suppress occurrence of vibration, the drum washingmachine is useful as a household washing machine used in a quietenvironment.

1. A drum washing machine comprising a water tub (10), a rotating tub(14) provided in the water tub (10) to be rotated about a transverseaxis, elastic supporting means (11) for elastically supporting the watertub (10), and an auxiliary baffle (23) provided on an inner peripheralwall of the rotating tub (14) so as to be close to one of both axial endplates of the rotating tub (14) and spaced away from the other end plateof the rotating tub (14), the auxiliary baffle (23) extending in adirection of axis of the rotating tub (14), characterized in that theauxiliary baffle (23) moves laundry in the rotating tub (14) near acenter of gravity of a member of vibration system applying load to theelastic supporting means (11).
 2. The drum washing machine according toclaim 1, characterized in that the auxiliary baffle (23) has an inclinedface (23 b) inclined at the inner peripheral wall side from one endplate side of the rotating tub (14) to the other end plate side.
 3. Thedrum washing machine according to claim 1, characterized in that therotating tub (14) has a rotational shaft comprising an inclined shafthaving both ends one of which is located higher than the other, and theauxiliary baffle is provided on the inner peripheral wall of therotating tub so as to be close to said one end plate located higher thanthe other.
 4. The drum washing machine according to claim 1,characterized in that the baffle (23) includes a first baffle close toone of the end plates of the rotating tub (14) and a second baffle closeto the other end plate of the rotating tub (14), and the first andsecond baffles are opposed to each other in the direction of axis of therotating tub (14).
 5. The drum washing machine according to claim 4,characterized in that the center of gravity of the vibration systemmember is located nearer to the one end plate side than an axial centerof the rotating tub (14), and the second baffle is larger than the firstbaffle.
 6. The drum washing machine according to claim 1, furthercomprising a plurality of main baffles (20, 21, 22) provided on an axialcenter of the inner peripheral wall of the rotating tub (14) so as toextend in a direction of axis of the rotating tub (14), characterized inthat a peripheral position of the auxiliary baffle (23) with respect tothe rotating tub (14) differs from peripheral positions of the mainbaffles (20, 21, 22) with respect to the rotating tub (14).
 7. The drumwashing machine according to claim 6, characterized in that theauxiliary baffle (23) and the main baffles (20, 21, 22) are disposed soas to be spaced peripherally away from each other with respect to therotating tub (14).
 8. The drum washing machine according to claim 1,characterized in that the auxiliary baffle (23) extends so as to betapered from one of the end plates of the rotating tub (14) toward theother end plate of the rotating tub (14).
 9. The drum washing machineaccording to claim 1, characterized in that the auxiliary baffle (23)has a radial dimension set at 30 mm or above with respect to therotating tub (14).
 10. The drum washing machine according to claim 1,characterized in that the auxiliary baffle (23) is disposed in a regionof the inner peripheral wall of the rotating tub (14) extending from oneof the end plates to a center of gravity of the member of vibrationsystem, and the auxiliary baffle (23) has an axial dimension set to benot less than one eighth of an axial dimension of the rotating tub (14).